Endoscopic and laparoscopic surgical instruments are often preferred over traditional open surgical devices since a smaller incision tends to reduce the post-operative recovery time and complications. The use of laparoscopic and endoscopic surgical procedures has been relatively popular and has provided additional incentive to develop the procedures further. In laparoscopic procedures, surgery is performed in the interior of the abdomen through a small incision. Similarly, in endoscopic procedures, surgery is performed in any hollow viscus of the body through narrow endoscopic tubes inserted through small entrance wounds in the skin.
Laparoscopic and endoscopic procedures generally require that the surgical region be insufflated. Accordingly, any instrumentation inserted into the body must be sealed to ensure that gases do not enter or exit the body through the incision. Moreover, laparoscopic and endoscopic procedures often require the surgeon to act on organs, tissues and/or vessels far removed from the incision. Thus, instruments used in such procedures are typically long and narrow while being functionally controllable from a proximal end of the instrument.
Significant development has gone into a range of endoscopic surgical instruments that are suitable for precise placement of a distal end effector at a desired surgical site through a cannula of a trocar. These distal end effectors engage the tissue in a number of ways to achieve a diagnostic or therapeutic effect (e.g., endocutter, grasper, cutter, staplers, clip applier, access device, drug/gene therapy delivery device, and energy device using ultrasound, RF, laser, etc.).
Known surgical staplers include an end effector that simultaneously makes a longitudinal incision in tissue and applies lines of staples on opposing sides of the incision. The end effector includes a pair of cooperating jaw members that, if the instrument is intended for endoscopic or laparoscopic applications, are capable of passing through a cannula passageway. One of the jaw members receives a staple cartridge having at least two laterally spaced rows of staples. The other jaw member defines an anvil having staple-forming pockets aligned with the rows of staples in the cartridge. The instrument includes a plurality of reciprocating wedges which, when driven distally, pass through openings in the staple cartridge and engage drivers supporting the staples to effect the firing of the staples toward the anvil.
Generally, a single closing stroke followed by a single firing stroke is a convenient and efficient way to perform severing and stapling. However, in some instances, multiple firing strokes are desirable. For example, surgeons select a length of staple cartridge for the desired length of the cut from a range of jaw sizes. Longer staple cartridges require a longer firing stroke. Thus, to effect the firing, a hand-squeezed trigger is required to exert a larger force for these longer staple cartridges in order to sever more tissue and drive more staples as compared to a shorter staple cartridge. It would be desirable for the amount of force to be lower and comparable to shorter cartridges so as not to exceed the hand strength of some surgeons. In addition, some surgeons, not familiar with the larger staple cartridges, may become concerned that binding or other malfunction may occur when an unexpectedly higher force is required.
In co-pending and commonly-owned U.S. Pat. Appl. Publ. 2005/0067457 A1, Ser. No. 10/673,929, “SURGICAL STAPLING INSTRUMENT WITH MULTISTROKE FIRING INCORPORATING AN ANTI-BACKUP MECHANISM” to Shelton et al. filed on Sep. 29, 2003, the disclosure of which is hereby incorporated by reference in its entirety, an advantageous anti-backup mechanism mechanically disengages as a firing member distally moves during each firing stroke and then engages as the firing trigger is released between firing strokes, preventing inadvertent retraction. Upon full firing travel, a mechanical linkage is tripped that disengages the anti-backup mechanism, allowing a retraction spring to retract the firing member. Thereby, the advantages of multiple firing strokes were realized in combination with automatic retraction.
More recently, a similar anti-backup mechanism is described in two U.S. patent application Ser. Nos. 11/052,387 entitled “SURGICAL STAPLING INSTRUMENT INCORPORATING A MULTI-STROKE FIRING MECHANISM WITH RETURN SPRING ROTARY MANUAL RETRACTION SYSTEM” to Shelton et al., and U.S. patent application Ser. No. 11/052,632 entitled “SURGICAL STAPLING INSTRUMENT INCORPORATING A FIRING MECHANISM HAVING A LINKED RACK TRANSMISSION” to Swayze et al., both filed on 8 Feb. 2005, the disclosure of both being hereby incorporated by reference in its entirety.
While these mechanically controlled anti-backup mechanisms provide significant clinical utility, it is desirable to provide an alternate approach to preventing inadvertent retraction that allows for additional functionality.
Consequently, a significant need exists for an improved surgical stapling and severing instrument that performs multistroke firing for increased firing travel and/or reduced force to fire with a reliable and configurable prevention of inadvertent firing retraction between strokes.